A heat source detection device that detects a heat source in a prescribed detection area detects whether or not a heat source exists, the size of a heat source, etc. based on a temperature distribution in the detection area obtained by converting an electric output (sensor output) output from an infrared image sensor into a temperature. As a method of highly accurately measuring a temperature of a heat source in this type of heat source detection devices, a method is known that corrects a sensor output based on the sensitivity of each photodetector in an infrared image sensor so as to suppress differences in temperatures caused by variations in sensor outputs.
Also, a method is known in which intensity distributions of a plurality of types of infrared rays radiated from a subject (heat source) of different wavelength bands are detected so as to calculate a surface temperature of the subject based on the detected intensity distributions, and thereby the accuracy in measuring the surface temperature is improved. As a method of calculating a surface temperature of a subject based on intensity distributions of a plurality of types of infrared rays, a method is known in which intensity distributions of three types of infrared rays are detected so as to calculate the surface temperature by using a method referred to as a trichromatic colorimetry (see Document 1 for example). Also, as another method, a method is known in which a temperature of a subject is highly accurately measured based on a ratio between two different types of outputs of different wavelength bands output from an infrared image sensor (see Document 2 for example).
Document 1: Japanese Laid-open Patent Publication No. 2009-047611
Document 2: Japanese Laid-open Patent Publication No. 2004-085319